BBC news reports that a ferryboat accident in Baltimore, which killed five, was caused in part by the fact that Americans weigh so much more, on average, than they used to. The water taxi was built using 1940s weight guidelines, which assumed the weight of an average rider was 140 pounds. Just a few decades later, the average is closer to 170. In the end the boat was carrying 700 pounds more than its maximum limit, making it too low in the water to operate safely in bad weather.
A simple solution has been proposed: markings on the hull could show how low a boat is in the water.